Doxygen replaces the name of the first enumeration in a C++11 strongly typed anonymous enumeration with the the string "__pad0__". This behavior can be reproduced by attempting to generate HTML documentation for the following enumeration:

enum: unsigned int
{
    FOO,
    BAR
};

The documentation for this enumeration will replace FOO with __pad0__. Please note this behavior does not seem to occur in strongly typed named enumerations. For example, the following will generate correct documentation:

enum Foo: unsigned int
{
    BAR,
    BAZ
};

This behavior has been tested in Doxygen version 1.8.2 on Mac OS X.